Food-deprived Mice Research Articles

Growth Hormone Receptor in Lateral Hypothalamic Neurons Is Required for Increased Food-Seeking Behavior during Food Restriction in Male Mice.

Growth hormone (GH) action in the brain regulates neuroendocrine axes, energy and glucose homeostasis, and several neurological functions. The lateral hypothalamic area (LHA) contains numerous neurons that respond to a systemic GH injection by expressing the phosphorylated STAT5, a GH receptor (GHR) signaling marker. However, the potential role of GHR signaling in the LHA is unknown. In this study, we demonstrated that ∼70% of orexin- and leptin receptor (LepR)-expressing neurons in the LHA are responsive to GH. Male mice carrying inactivation of the Ghr gene in the LHA were generated via bilateral injections of an adeno-associated virus. In ad libitum-fed mice, GHR ablation in LHA neurons did not significantly change energy and glucose homeostasis. Subsequently, mice were subjected to 5 d of 40% food restriction. Food restriction decreased body weight, energy expenditure, and carbohydrate oxidation. These effects were similarly observed in control and LHAΔGHR mice. While food-deprived control mice progressively increased ambulatory/exploratory activity and food-seeking behavior, LHAΔGHR mice did not show hyperactivity induced by food restriction. GHR ablation in the LHA reduced the percentage of orexin neurons expressing c-Fos during food restriction. Additionally, an acute GH injection increased the expression of c-Fos in LHAORX neurons. Inactivation of Ghr in LepR-expressing cells did not prevent hyperactivity in food-deprived mice, whereas whole-brain Ghr knock-out mice showed reduced ambulatory activity during food restriction. Our findings indicate that GHR signaling in the LHA regulates the activity of orexin neurons and is necessary to increase food-seeking behavior in food-deprived male mice.

The GLP-1 Receptor Agonist Liraglutide Decreases Primary Bile Acids and Serotonin in the Colon Independently of Feeding in Mice.

Liraglutide, a glucagon-like peptide 1 analog used to treat type 2 diabetes and obesity, is a potential new treatment modality for bile acid (BA) diarrhea. Here, we show that administration of liraglutide significantly decreased total BAs, especially the primary BAs, including cholic acid, chenodeoxycholic acid, taurocholic acid, taurochenodeoxycholic acid, glycocholic acid, and β-muricholic acid, in the liver and feces. In addition, liraglutide significantly decreased tryptophan metabolites, including L-tryptophan, serotonin, 5-hydroxy indole-3-acetic acid, L-kynurenine, and xanthurenic acid, in the colon, whereas it significantly increased indole-3-propionic acid. Moreover, the administration of liraglutide remarkably decreased the expression of apical sodium-dependent bile acid transporter, which mediates BA uptake across the apical brush border member in the ileum, ileal BA binding protein, and fibroblast growth factor 15 in association with decreased expression of the BA-activated nuclear receptor farnesoid X receptor and the heteromeric organic solute transporter Ostα/β, which induces BA excretion, in the ileum. Liraglutide acutely decreased body weight and blood glucose levels in association with decreases in plasma insulin and serotonin levels in food-deprived mice. These findings suggest the potential of liraglutide as a novel inhibitor of primary BAs and serotonin in the colon.

Photobiomodulation Therapy Restores Olfactory Function Impaired by Photothrombosis in Mouse Olfactory Bulb

An ischemic stroke typically accompanies numerous disorders ranging from somatosensory dysfunction to cognitive impairments, inflicting patients with various neurologic symptoms. Among pathologic outcomes, post-stroke olfactory dysfunctions are frequently observed. Despite the well-known prevalence, therapy options for such compromised olfaction are limited, likely due to the complexity of olfactory bulb architecture, which encompasses both the peripheral and central nervous systems. As photobiomodulation (PBM) emerged for treating ischemia-associated symptoms, the effectiveness of PBM on stroke-induced impairment of olfactory function was explored. Novel mouse models with olfactory dysfunctions were prepared using photothrombosis (PT) in the olfactory bulb on day 0. The post-PT PBM was performed daily from day 2 to day 7 by irradiating the olfactory bulb via an 808 nm laser with a fluence of 40 J/cm2 (325 mW/cm2 for 2 smin per day). The buried food test (BFT) was used to score behavioral acuity in food-deprived mice to assess the olfactory function before PT, after PT, and after PBM. Histopathological examinations and cytokine assays were performed on the mouse brains harvested on day 8. The results from BFT were specific to an individual, with positive correlations between the baseline latency time measured before PT and its alteration at the ensuing stages for both the PT and PT + PBM groups. Also, the correlation analysis in both groups showed highly similar, significant positive relationships between the early and late latency time change independent of PBM, implicating a common recovery mechanism. Particularly, PBM treatment accelerated the recovery of impaired olfaction following PT by suppressing inflammatory cytokines and enhancing both glial and vascular factors (e.g., GFAP, IBA-1, and CD31). PBM therapy during the acute phase of ischemia improves the compromised olfactory function by modulating microenvironments and inflammation status of the affected tissue.

Orexin induces the production of an endocannabinoid-derived lysophosphatidic acid eliciting hypothalamic synaptic loss in obesity

ObjectiveOrexin-A (OX-A) is a neuropeptide produced selectively by neurons of the lateral hypothalamus. It exerts powerful control over brain function and physiology by regulating energy homeostasis and complex behaviors linked to arousal. Under conditions of chronic or acute brain leptin signaling deficiency, such as in obesity or short-term food deprivation, respectively, OX-A neurons become hyperactive and promote hyperarousal and food seeking. However, this leptin-dependent mechanism is still mostly unexplored. The endocannabinoid 2-arachidonoyl-glycerol (2-AG) is known to be implicated in food consumption by promoting hyperphagia and obesity, and we and others demonstrated that OX-A is a strong inducer of 2-AG biosynthesis. Here, we investigated the hypothesis that, under acute (6 h fasting in wt mice) or chronic (in ob/ob mice) hypothalamic leptin signaling reduction, OX-A-induced enhancement of 2-AG levels leads to the production of the 2-AG-derived 2-arachidonoyl-sn-glycerol-3-phosphate (2-AGP), a bioactive lipid belonging to the class of lysophosphatidic acids (LPAs), which then regulates hypothalamic synaptic plasticity by disassembling α-MSH anorexigenic inputs via GSK-3β-mediated Tau phosphorylation, ultimately affecting food intake. MethodsWe combined cell-type-specific morphological (CLEM and confocal microscopy), biochemical, pharmacological, and electrophysiological techniques to dissect the leptin- and OX-A/2-AGP-mediated molecular pathways regulating GSK-3β-controlled pT231-Tau production at POMC neurons of obese ob/ob and wild-type (wt) lean littermate mice and in an in vitro model of POMC neurons such as mHypoN41 neurons (N41). Results2-AGP is overproduced in the hypothalamus of obese leptin-deficient, or lean 6 h food-deprived mice, and promotes food intake by reducing α-MSH-expressing synaptic inputs to OX-A neurons via lysophosphatidic acid type-1 receptor (LPA1-R) activation, and pT231-Tau accumulation in α-MSH projections. This effect is due to the activation of the Pyk2-mediated pTyr216-GSK3β pathway and contributes to further elevating OX-A release in obesity. Accordingly, we found a strong correlation between OX-A and 2-AGP levels in the serum of obese mice and of human subjects. ConclusionsHypothalamic feeding pathways are endowed with 2-AGP-mediated synaptic plasticity according to their inherent functional activities and the necessity to adapt to changes in the nutritional status. These findings reveal a new molecular pathway involved in energy homeostasis regulation, which could be targeted to treat obesity and related disturbances.

GHSR controls food deprivation-induced activation of CRF neurons of the hypothalamic paraventricular nucleus in a LEAP2-dependent manner.

Prolonged fasting is a major challenge for living organisms. An appropriate metabolic response to food deprivation requires the activation of the corticotropin-releasing factor-producing neurons of the hypothalamic paraventricular nucleus (PVHCRF neurons), which are a part of the hypothalamic-pituitary-adrenal axis (HPA), as well as the growth hormone secretagogue receptor (GHSR) signaling, whose activity is up- or down-regulated, respectively, by the hormones ghrelin and the liver-expressed antimicrobial peptide 2 (LEAP2). Since ghrelin treatment potently up-regulates the HPA axis, we studied the role of GHSR in mediating food deprivation-induced activation of the PVHCRF neurons in mice. We estimated the activation of the PVHCRF neurons, using immuno-staining against CRF and the marker of neuronal activation c-Fos in brain sections, and assessed plasma levels of corticosterone and glucose in different pharmacologically or genetically manipulated mouse models exposed, or not, to a 2-day food deprivation protocol. In particular, we investigated ad libitum fed or food-deprived male mice that: (1) lacked GHSR gene expression, (2) had genetic deletion of the ghrelin gene, (3) displayed neurotoxic ablation of the hypothalamic arcuate nucleus, (4) were centrally treated with an anti-ghrelin antibody to block central ghrelin action, (5) were centrally treated with a GHSR ligand that blocks ghrelin-evoked and constitutive GHSR activities, or (6) received a continuous systemic infusion of LEAP2(1-12). We found that food deprivation results in the activation of the PVHCRF neurons and in a rise of the ghrelin/LEAP2 molar ratio. Food deprivation-induced activation of PVHCRF neurons required the presence and the signaling of GHSR at hypothalamic level, but not of ghrelin. Finally, we found that preventing the food deprivation-induced fall of LEAP2 reverses the activation of the PVHCRF neurons in food-deprived mice, although it has no effect on body weight or blood glucose. Food deprivation-induced activation of the PVHCRF neurons involves ghrelin-independent actions of GHSR at hypothalamic level and requires a decrease of plasma LEAP2 levels. We propose that the up-regulation of the actions of GHSR associated to the fall of plasma LEAP2 level are physiologically relevant neuroendocrine signals during a prolonged fasting.

Role of linkage between cerebral activity and baroreflex control of heart rate via central vasopressin V1a receptors in food-deprived mice.

We previously reported that cerebral activation at the onset of voluntary locomotion suppressed baroreflex control of heart rate (HR) and increased arterial pressure via vasopressin V1a receptors in the brain. Here, we examined whether these responses were associated with food seeking, a motivated behavior, using free-moving wild type (WT, n = 10), V1a receptor knockout (KO, n = 9), and wild-type mice locally infused with a V1a receptor antagonist into the nucleus tractus solitarii (BLK, n = 10). For three consecutive days, mice were fed ad libitum (Fed), food deprived (FD), and refed (RF) under a dark/light cycle (1900/0700). Food was removed on day 2 and restored on day 3 at 1800. Throughout the protocol, cerebral activity was determined from the power density ratio of θ- to δ-wave band (θ/δ) by electroencephalogram every 4 s. Baroreflex was evaluated by the cross-correlation function [R(t)] between changes in HR and arterial pressure every 4 s. The cerebro-baroreflex linkage was then evaluated by the cross-correlation function between θ/δ and R(t). Behavior was recorded with CCD camera. We found that cerebro-baroreflex linkage, enhanced in WT at night after FD (P = 0.006), returned to Fed level after RF (P = 0.68). Similarly, food-seeking behavior increased after FD to a level twofold higher than during Fed (P < 0.001) and returned to Fed level after RF (P = 0.54). However, none of these changes occurred in KO or BLK (P > 0.11). Thus, the suppression of baroreflex control of HR linked with cerebral activation via central V1a receptors might play an important role at the onset of motivated behaviors, such as food seeking induced by FD.NEW & NOTEWORTHY Motivated behaviors, characterized by goal-directed and persistent movements, are indispensable for living. However, how cerebro-cardiovascular adjustment occurs during such behaviors remains unknown. By focusing on food-seeking behavior in a food-deprived condition using free-moving mice, we found that this condition enhanced the linkage between cerebral activation and suppression of baroreflex control of heart rate through central vasopressin V1a receptors, making it easier to start motivated behaviors by enhancing pressor response.

ATF4-Mediated Upregulation of REDD1 and Sestrin2 Suppresses mTORC1 Activity during Prolonged Leucine Deprivation

Background:The protein kinase target of rapamycin (mTOR) in complex 1 (mTORC1) is activated by amino acids and in turn upregulates anabolic processes. Under nutrient-deficient conditions, e.g., amino acid insufficiency, mTORC1 activity is suppressed and autophagy is activated. Intralysosomal amino acids generated by autophagy reactivate mTORC1. However, sustained mTORC1 activation during periods of nutrient insufficiency would likely be detrimental to cellular homeostasis. Thus, mechanisms must exist to prevent amino acids released by autophagy from reactivating the kinase. Objective:The objective of the present study was to test whether mTORC1 activity is inhibited during prolonged leucine deprivation through ATF4-dependent upregulation of the mTORC1 suppressors regulated in development and DNA damage response 1 (REDD1) and Sestrin2. Methods:Mice (8 wk old; C57Bl/6 × 129SvEV) were food deprived (FD) overnight and one-half were refed the next morning. Mouse embryo fibroblasts (MEFs) deficient in ATF4, REDD1, and/or Sestrin2 were deprived of leucine for 0–16 h. mTORC1 activity and ATF4, REDD1, and Sestrin2 expression were assessed in liver and cell lysates. Results:Refeeding FD mice resulted in activation of mTORC1 in association with suppressed expression of both REDD1 and Sestrin2 in the liver. In cells in culture, mTORC1 exhibited a triphasic response to leucine deprivation, with an initial suppression followed by a transient reactivation from 2 to 4 h and a subsequent resuppression after 8 h. Resuppression occurred concomitantly with upregulated expression of ATF4, REDD1, and Sestrin2. However, in cells lacking ATF4, neither REDD1 nor Sestrin2 expression was upregulated by leucine deprivation, and resuppression of mTORC1 was absent. Moreover, in cells lacking either REDD1 or Sestrin2, mTORC1 resuppression was attenuated, and in cells lacking both proteins resuppression was further blunted. Conclusions:The results suggest that leucine deprivation upregulates expression of both REDD1 and Sestrin2 in an ATF4-dependent manner, and that upregulated expression of both proteins is involved in resuppression of mTORC1 during prolonged leucine deprivation.

Analysis of inequality aversion in mice using stress-induced hyperthermia

Humans have a sense of fairness and consequently have an aversion to inequality condition. Recently, animal researchers have suggested that some non-human animals also exhibit an aversion to inequality. This experiment used stress-induced hyperthermia (SIH) to examine inequality aversion in mice. Aversion was analyzed using inequitable restraint stress in Experiment 1. The mice that were restrained, but had free cage mates (disadvantageous inequality) displayed SIH. In contrast, free mice that had restrained cage mates (advantageous inequality) did not show SIH. Inequitable food delivery was used to induce SIH in Experiment 2. Food deprived mice who were surrounded by cage mates who were consuming food (disadvantageous inequality) displayed SIH. The mice that received food and were surrounded by food-deprived cage mates (advantageous inequality) also showed some increase in body temperature, but the increase was not significantly higher than that in the equality condition (where all mice received food). Pre-feeding of the test mice attenuated SIH in the disadvantageous condition suggesting that satisfied mice do not display disadvantageous inequality aversion. These results showed disadvantageous inequality aversion in mice in both negative (restraint) and positive (food) situations but not advantageous inequality aversion.

Growth hormone regulates neuroendocrine responses to weight loss via AgRP neurons

Weight loss triggers important metabolic responses to conserve energy, especially via the fall in leptin levels. Consequently, weight loss becomes increasingly difficult with weight regain commonly occurring in most dieters. Here we show that central growth hormone (GH) signaling also promotes neuroendocrine adaptations during food deprivation. GH activates agouti-related protein (AgRP) neurons and GH receptor (GHR) ablation in AgRP cells mitigates highly characteristic hypothalamic and metabolic adaptations induced by weight loss. Thus, the capacity of mice carrying an AgRP-specific GHR ablation to save energy during food deprivation is impaired, leading to increased fat loss. Additionally, administration of a clinically available GHR antagonist (pegvisomant) attenuates the fall of whole-body energy expenditure of food-deprived mice, similarly as seen by leptin treatment. Our findings indicate GH as a starvation signal that alerts the brain about energy deficiency, triggering key adaptive responses to conserve limited fuel stores.

Hypothalamic Neurons that Regulate Feeding Can Influence Sleep/Wake States Based on Homeostatic Need

Eating and sleeping represent two mutually exclusive behaviors that satisfy distinct homeostatic needs. Because an animal cannot eat and sleep at the same time, brain systems that regulate energy homeostasis are likely to influence sleep/wake behavior. Indeed, previous studies indicate that animals adjust sleep cycles around periods of food need and availability. Furthermore, hormones that affect energy homeostasis also affect sleep/wake states: the orexigenic hormone ghrelin promotes wakefulness, and the anorexigenic hormones leptin and insulin increase the duration of slow-wave sleep. However, whether neural populations that regulate feeding can influence sleep/wake states is unknown. The hypothalamic arcuate nucleus contains two neuronal populations that exert opposing effects on energy homeostasis: agouti-related protein (AgRP)-expressing neurons detect caloric need and orchestrate food-seeking behavior, whereas activity in pro-opiomelanocortin (POMC)-expressing neurons induces satiety. We tested the hypotheses that AgRP neurons affect sleep homeostasis by promoting states of wakefulness, whereas POMC neurons promote states of sleep. Indeed, optogenetic or chemogenetic stimulation of AgRP neurons in mice promoted wakefulness while decreasing the quantity and integrity of sleep. Inhibition of AgRP neurons rescued sleep integrity in food-deprived mice, highlighting the physiological importance of AgRP neuron activity for the suppression of sleep by hunger. Conversely, stimulation ofPOMC neurons promoted sleep states and decreased sleep fragmentation in food-deprived mice. Interestingly, we also found that sleep deprivation attenuated the effects of AgRP neuron activity on food intake and wakefulness. These results indicate that homeostatic feeding neurons can hierarchically affect behavioral outcomes, depending on homeostatic need.

Characterization of changes of pain behavior and signal transduction system in food-deprived mice

ABSTRACTFasting in general causes several metabolic changes. In the present study, we examined the possible changes of several types of nociception during the food deprivation were investigated in mice. After the mice were forced into the fasting for 12, 24, or 48 h, the changes of nociception were measured by the tail-flick, writhing, formalin or von-frey tests. We found that the nociceptive behavior induced by intraperitoneally (i.p.) administered acetic acid (writhing response) or intraplantar injection of 5% formalin into the hind-paw were reduced in fasted group. In addition, the tail-flick response and threshold for nociception in mechanical von-frey test were also elevated in fasted group. Moreover, the p-CREB and p-ERK levels in the dorsal root ganglia (DRG) and the spinal cord were reduced in food-deprived group. Furthermore, p-AMPKα1 expressions in DRG and the spinal cord were up-regulated, whereas p-mTOR in DRG and the spinal cord was down-regulated in food-deprived group. Our results suggest that the chemical, mechanical, and thermal nociceptions appear to be reduced in a food-deprived mouse group. Additionally, reduction of nociception in food-deprived group appears to be closely associated with the expressions of several signal transduction molecules such as ERK, CREB, AMPKα1 and mTOR proteins in DRG and the spinal cord.

Buried Food-seeking Test for the Assessment of Olfactory Detection in Mice.

The sense of smell allows animals to discriminate a large number of volatile environmental chemicals. Such chemical signaling modulates the behavior of several species that depend on odorant compounds to locate food, recognize territory, predators, and toxic compounds. Olfaction also plays a role in mate choice, mother-infant recognition, and social interaction among members of a group. A key assay to assess the ability to smell odorants is the buried food-seeking test, which checks whether the food-deprived mice can find the food pellet hidden beneath the bedding in the animal's cage. The main parameter observed in this test is the latency to uncover a small piece of chow, cookie, or other pleasant food, hidden beneath a layer of cage bedding, within a limited amount of time. It is understood that food-restricted mice which fail to use odor cues to locate food within a given time period are likely to have deficits in olfactory abilities. Investigators who used the buried food test, or versions of the buried food test, demonstrated that it is possible to evaluate olfactory deficits in different models of murine studies (Alberts and Galef, 1971; Belluscio et al., 1998 ; Luo et al., 2002 ; Li et al., 2013 ). We have recently used this assay to demonstrate that olfactory-specific Ric-8B knock-out mice (a guanine nucleotide exchange factor that interacts with olfactory-specific G-protein) show an impaired sense of smell ( Machado et al., 2017 ). Here we describe the protocol of the buried food-seeking test, as adopted in our assays.

Investigations of octylglyceryl dextran-graft-poly(lactic acid) nanoparticles for peptide delivery to the brain.

Develop modified dextran nanoparticles showing potential to assist with drug permeation across the blood-brain barrier for the delivery of neuropeptides. Nanoparticles loaded by emulsification with model macromolecular actives were characterized in terms of stability, cytotoxicity and drug-release behavior. Peptide-loaded nanoformulations were tested in an in vivo trout model and in food-deprived mice. Nanoformulations loaded with model peptides showed good stability and appeared nontoxic in low concentration against human brain endothelial cells. They were found to preserve the bioactivity of loaded peptides (angiotensin II) as demonstrated in vivo using a trout model, and to induce a transient reduction of food consumption in mice when loaded with an anorexigenic octaneuropeptide. Octylglyceryl dextran-graft-poly(lactic acid) nanoparticles formulated by emulsification demonstrate potential for peptide delivery.

Endothelial HIF-1α Enables Hypothalamic Glucose Uptake to Drive POMC Neurons.

Glucose is the primary driver of hypothalamic proopiomelanocortin (POMC) neurons. We show that endothelial hypoxia-inducible factor 1α (HIF-1α) controls glucose uptake in the hypothalamus and that it is upregulated in conditions of undernourishment, during which POMC neuronal activity is decreased. Endothelium-specific knockdown of HIF-1α impairs the ability of POMC neurons to adapt to the changing metabolic environment in vivo, resulting in overeating after food deprivation in mice. The impaired functioning of POMC neurons was reversed ex vivo or by parenchymal glucose administration. These observations indicate an active role for endothelial cells in the central control of metabolism and suggest that central vascular impairments may cause metabolic disorders.

Effect of food deprivation or short-term Western diet feeding on BDNF protein expression in the hypothalamic arcuate, paraventricular, and ventromedial nuclei.

Mutations in the brain-derived neurotrophic factor (BDNF) gene are associated with human obesity, and BDNF has potent inhibitory effects on eating and body weight. Little is known about the effects of energy balance manipulations on BDNF protein in the hypothalamus, though this brain region is critical for regulation of feeding and body weight and has high levels of BDNF. Here we investigated the effects of negative and positive energy status on BDNF protein levels in the arcuate (ARC), paraventricular, and ventromedial (VMH) hypothalamic nuclei and the ectorhinal cortex. To achieve this, mice were food deprived for 48 h or fed a Western diet (WD), a restricted amount of WD, or chow for 6 h, 48 h, 1 wk, or 3 wk. BDNF protein levels were estimated as the number of neurons in each brain region that exhibited BDNF-like immunoreactivity. Food deprivation decreased BDNF protein (and mRNA) expression in the ARC compared with fed mice (32%). In contrast, 1 wk of WD consumption increased BDNF protein expression in the VMH compared with chow or restricted WD feeding (40%) and, unexpectedly, increased BDNF protein in the ectorhinal cortex (20%). Furthermore, of the diet conditions and durations tested, only 1 wk of WD consumption was associated with both hyperphagia and excess weight, suggesting that effects of one or both contributed to the changes in BDNF levels. The decrease in ARC BDNF may support increased feeding in food-deprived mice, whereas the increase in the VMH may moderate overeating in WD-fed mice.

Abstract # 1747 Activation of indoleamine 2,3 dioxygenase does not mediate inflammation-induced reductions in incentive motivation

While inflammation is implicated in the development of depression, the neurobiological mechanisms remain elusive. One of the reasons for this is the complexity of depression. To move forward we have decided to deconstruct depression into basic neurobiological units and focus on incentive motivation and anhedonia. Using an operant conditioning task in which mice have the choice between a high effort/high reward and a low effort/low reward mode of response we demonstrated inflammation affects willingness to exert an effort for the reward but does not reduce the sensitivity to the reward. To assess the importance of activation of indoleamine 2,3 dioxygenase (IDO1) in these effects, we compared IDO1-deficient to wild type mice. In accordance with our previous results (Vichaya et al, Neuropsychopharmacology 2014) wild type mice responded to lipopolysaccharide (LPS, 0.33 mg/kg intraperitoneal 24 h before) by a reduction in total responses and an increase in percent chocolate pellets earned. The same response to LPS was observed in IDO1 KO mice. To further assess motivation, food-deprived mice were submitted to a restricted schedule of food delivery that resulted in an increase in locomotor activity just before the expected delivery of food. This food-related anticipatory activity was decreased in the same manner by LPS in wild type and IDO1 KO mice. These findings indicate that inflammation-induced deficits in incentive motivation are not mediated by IDO1 activation.

Opioid systems in the lateral hypothalamus regulate feeding behavior through orexin and GABA neurons

The hypothalamus controls feeding behavior. Since central opioid systems may regulate feeding behavior, we examined the role of μ-, δ- and κ-opioid receptors in the lateral hypothalamus (LH), the hunger center, in feeding behavior of mice. Non-selective (naloxone; 3mg/kg, s.c.) and selective μ- (β-funaltrexamine, β-FNA; 10mg/kg, s.c.), δ- (naltrindole; 3mg/kg, s.c.) and κ- (norbinaltorphimine, norBNI; 20mg/kg, s.c.) opioid receptor antagonists significantly decreased food intake in food-deprived mice. The injection of naloxone (20μg/side) into the LH significantly decreased food intake whereas the injection of naloxone (20μg/side) outside of the LH did not affect food intake. The injection of β-FNA (2μg/side), naltrindole (1μg/side) or norBNI (2μg/side) into the LH significantly decreased food intake. Furthermore, all these antagonists significantly decreased the mRNA level of preproorexin, but not those of other hypothalamic neuropeptides. In addition, the injection of the GABAA receptor agonist muscimol (5μg/side) into the LH significantly decreased food intake, and this effect was abolished by the GABAA receptor antagonist bicuculline (50μg/side). Muscimol (1mg/kg, i.p.) decreased the mRNA level of preproorexin in the hypothalamus. Naloxone (3mg/kg, s.c.) significantly increased the GABA level in the LH and both bicuculline and the GABA release inhibitor 3-mercaptopropionic acid (3-MP, 5μg/side) attenuated the inhibitory effect of naloxone on feeding behavior. 3-MP also attenuated the effects of β-FNA and norBNI, but not that of naltrindole. These results show that opioid systems in the LH regulate feeding behavior through orexin neurons. Moreover, μ- and κ-, but not δ-, opioid receptor antagonists inhibit feeding behavior by activating GABA neurons in the LH.

Correction: Sirt1 Regulates Insulin Secretion by Repressing UCP2 in Pancreatic β Cells

The authors would like to clarify that the controls previously depicted in Figs ​Figs4E4E and ​and7A7A were for different experiments and were included in error. Fig 4 UCP2 is Up-Regulated in Sirt1 Knockdown Cells and in Sirt1 KO Mice. Fig 7 UCP2 mRNA or Protein Levels in Fed or Starved Wild-Type Mice. The correct control for Fig 4E was located and used to prepare a corrected figure. The correct control for the original Fig 7A could not be located; this panel has therefore been removed after a careful assessment and investigation determined that the result for which original Fig 7A was cited is supported elsewhere in this article, and that removal of this panel does not affect the conclusions of the paper. We have also taken this opportunity to provide new versions of several figures (Figs ​(Figs4,4, ​,5,5, ​,6,6, ​,7)7) in which gel/blot splices and a non-linear level adjustment were made but were not previously indicated or declared, or to replace incorrectly spliced gels/blots with the un-spliced originals. We also take the opportunity to correct two errors in the legend to Fig 6, first to remove a redundant and incorrect sentence, and second to address incorrect description of p values. Fig 5 Sirt1 Binds at the UCP2 Promoter and Represses the Gene. Fig 6 Knockdown of UCP2 in Sirt1 Knockdown Cells Restores Glucose-Induced Insulin Secretion. The text in the Results section titled “UCP2 Levels Increase in Food-Deprived Mice” has been edited to accommodate the removal of the original Fig 7A and the relabeling of Fig 7B, 7C and 7D as Fig 7A, 7B and 7C, respectively. The corrected text and Figs ​Figs4,4, ​,5,5, ​,66 and ​and77 are provided here.

Pharmacologic stimulation of central GLP-1 receptors has opposite effects on the alterations of plasma FGF21 levels induced by feeding and fasting

Fibroblast growth factor 21 (FGF21) functions as an endocrine hormone to regulate energy metabolism. Circulating FGF21 is derived from the liver and is produced in response to alterations of nutritional status. Here we show the effects of liraglutide, a human glucagon-like-peptide-1 (GLP-1) receptor agonist, injected into the third cerebral ventricle on body weight and plasma FGF21 levels in free-feeding mice, food-deprived mice, and mice provided 1g after the injection. In free-feeding mice, liraglutide (5–100μg/kg) injected into the third cerebral ventricle suppressed food intake and body weight after 24h in a dose-dependent manner. Liraglutide (50 and 100μg/kg) significantly increased plasma FGF21 levels and hepatic FGF21 expression, whereas smaller doses (5 and 10μg/kg) had no effect. In food-deprived mice, body weight did not differ significantly between the saline control and liraglutide-treated groups, but liraglutide (100μg/kg) significantly decreased plasma FGF21 levels at 24h compared with the saline control. In mice provided 1g food, body weight did not differ significantly between the saline control and liraglutide-treated groups, but liraglutide (50μg/kg) significantly decreased plasma FGF21 levels at 24h compared with the saline control. These findings suggest that intracerebral injection of liraglutide decreases body weight by inhibiting food intake and increases plasma FGF21 levels in free-feeding mice, whereas it suppresses the elevations of plasma FGF21 levels induced by fasting or the restricted feeding. Thus, pharmacologic stimulation of central GLP-1 receptors has opposite effects on the alterations of plasma FGF21 levels induced by feeding and fasting.

Hunger States Control the Directions of Synaptic Plasticity via Switching Cell Type-Specific Subunits of NMDA Receptors.

It remains largely unknown whether and how hunger states control activity-dependent synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD). We here report that both LTP and LTD of excitatory synaptic strength within the appetite control circuits residing in hypothalamic arcuate nucleus (ARC) behave in a manner of hunger states dependence and cell type specificity. For instance, we find that tetanic stimulation induces LTP at orexigenic agouti-related protein (AgRP) neurons in ad libitum fed mice, whereas it induces LTD in food-deprived mice. In an opposite direction, the same induction protocol induces LTD at anorexigenic pro-opiomelanocortin (POMC) neurons in fed mice but weak LTP in deprived mice. Mechanistically, we also find that food deprivation increases the expressions of NR2C/NR2D/NR3-containing NMDA receptors (NMDARs) at AgRP neurons that contribute to the inductions of LTD, whereas it decreases their expressions at POMC neurons. Collectively, our data reveal that hunger states control the directions of activity-dependent synaptic plasticity by switching NMDA receptor subpopulations in a cell type-specific manner, providing insights into NMDAR-mediated interactions between energy states and associative memory. Significance statement: Based on the experiments performed in this study, we demonstrate that activity-dependent synaptic plasticity is also under the control of energy states by regulating NMDAR subpopulations in a cell type-specific manner. We thus propose a reversible memory configuration constructed from energy states-dependent cell type-specific bidirectional conversions of LTP and LTD. Together with the distinct functional roles played by NMDAR signaling in the control of food intake and energy states, these findings reveal a new reciprocal interaction between energy states and associative memory, one that might serve as a target for therapeutic treatments of the energy-related memory disorders or vice versa.